nebula: Auto enable as default overlay implementation

hosts/desktop/default.nix

@@ -37,7 +37,6 @@
     services = {
       auto-gc.enable = true;
       sound.enable = true;
-      nebula.enable = true;
       sshd.enable = true;
       syncthing = {
         enable = true;

hosts/laptop/default.nix

@@ -39,7 +39,6 @@
       auto-gc.enable = true;
       bluetooth.enable = true;
       sound.enable = true;
-      nebula.enable = true;
       sshd.enable = true;
       syncthing = {
         enable = true;

hosts/vps-monitor/default.nix

@@ -35,7 +35,6 @@
         onlyCleanRoots = true;
       };
 
-      nebula.enable = true;
       sshd.enable = true;
       dns.enable = true;
     };

hosts/vps-private/default.nix

@@ -39,7 +39,6 @@
           onlyCleanRoots = true;
         };
 
-        nebula.enable = true;
         sshd.enable = true;
         dns.enable = true;
 

hosts/vps-public/default.nix

@@ -38,7 +38,6 @@
           onlyCleanRoots = true;
         };
 
-        nebula.enable = true;
         sshd.enable = true;
 
         caddy.virtualHosts."dav.${sproutedDomain}" = {

modules/system/networking/overlay.nix

@@ -21,6 +21,7 @@ in
     prefixLength = lib.mkOption {
       type = lib.types.ints.between 0 32;
       default = cfg.networkCidr |> lib.splitString "/" |> lib.last |> lib.toInt;
+      readOnly = true;
     };
     domain = lib.mkOption {
       type = lib.types.nonEmptyStr;
@@ -61,5 +62,10 @@ in
         |> lib.filter (host: host.config.custom.services.dns.enable)
         |> lib.map (host: host.config.custom.networking.overlay.address);
     };
+
+    implementation = lib.mkOption {
+      type = lib.types.enum [ "nebula" ];
+      default = "nebula";
+    };
   };
 }

modules/system/services/nebula/default.nix

@@ -12,7 +12,9 @@ let
 in
 {
   options.custom.services.nebula = {
-    enable = lib.mkEnableOption "";
+    enable = lib.mkEnableOption "" // {
+      default = netCfg.overlay.implementation == "nebula";
+    };
 
     publicKeyPath = lib.mkOption {
       type = lib.types.path;